36 research outputs found

    Evaluating the viability of coastal wet grassland to a changing management regime through flood hazard modelling

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    The high-risk nature of low-lying coastal areas means that many are characterised by protective dikes, sea walls, and earthen embankments. Across Europe, such structures are employed to limit landward sea flooding and have been used historically to reclaim wetlands, many of which have since gained international protected habitat status. Sea level rise and storms threaten the future viability of fixed flood defences which will be overtopped with increasing frequency and, in extreme cases, breached. This raises questions surrounding defence maintenance and the fate of the reclaimed wetlands they encircle and support. One approach is to design defences with the expectation that they will be overtopped during extreme events, but that catastrophic failure as a result of breaching will be prevented. Such an approach was recently implemented at Blakeney Freshes, North Norfolk Coast, UK, an embanked area of reedbeds and coastal wet grassland. Lowering and widening of the Freshes embankment was undertaken following extensive breaching during the 5 December 2013 storm surge. In this paper we develop and apply a numerical model chain, comprising storm surge water levels, waves, and overtopping, to explore inundation extent, depth, and duration resulting from storm surge induced flooding under several sea level rise scenarios. Modelling results revealed that 99.5% of the flood volume of the 2013 event resulted from embankment breaching. Simulating the same storm event after embankment reprofiling shows that flooding of the Freshes is reduced by 97%, largely because the lower, wider embankments preclude breaching. However, under future sea level rise scenarios, storm surge induced overtopping results in increased inundation depths and drainage times, raising questions regarding the resilience of vegetation communities within the Freshes. By 2100 under the lowest SLR scenario, and by 2050 under the mid SLR scenario, over half of the Freshes will be inundated for >10 days, a potentially critical threshold for current wet grassland survival. Our findings suggest that while effective defence redesign may increase the viability of reclaimed wetland habitats in the short term, as sea levels rise, lengthened inundation durations may render these habitats increasingly vulnerable to ecosystem change under extreme events

    Assessment of ecosystem services of an urbanized tropical estuary with a focus on habitats and scenarios

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    Tropical estuaries are one of the most valuable ecosystems on the planet because of the number of ecosystem services they provide. The increasing anthropogenic pressure to which these estuaries are subject has caused a reduction in their natural capital stock. Therefore, the application of a pragmatic and rational ecosystem-based management approach to sustainably manage the multiple ecosystem services provided by this ecosystem is necessary. The aim of our study is to present an approach that combines prospective scenarios with habitat-based perspective to assess the supply capacity of ecosystem services, plus determine the impact of protected areas in an urbanized tropical estuary. The current situation and two scenarios were generated to evaluate the capacity of habitats to supply ecosystem services. This type of assessment will allow the decision makers to visualize the effect of their choices or the occurrence of events which might produce significant changes in the estuary. Thus, over time, measures can be taken to sustain the supply of ecosystem services. We determined that the establishment of protected areas have a positive impact; however, the effect is not the same for all of them. Consequently, indicating that actions such as community participation, research, education, management planning and infrastructure development must accompany the development of a protected area

    Long-term changes in metapopulation genetic structure: a quarter-century retrospective study on low-Arctic rock pool Daphnia

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    Population genetic surveys approximately 25 years apart examined the distribution and abundance of asexual clones of the freshwater zooplankter Daphnia pulex complex in rock pools near Churchill, Manitoba, Canada. In 1984–1985, melanic members of this species complex were present in 131 rock pools at this site, but were only detected in 90 of these pools in 2007–2008. Allozymic surveys conducted during these two time periods revealed that 59 per cent of these populations showed unchanged clonal composition. Total clonal replacement occurred in 8 per cent of the populations, while the others (33%) included a mixture of ‘resident’ clones and new ‘colonists’. We discuss these changes in light of shifts in biotic and abiotic factors. We also discuss the use of rock pool habitats as ‘sentinel’ systems for examining long-term environmental changes in the ecological genetics of aquatic organisms in the Arctic
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